Radiocondenser



June 15 1926.

J B. KIRBY ET AL RADIOCONDENSER Filed Au ust 5, 1925 I5- Sheets-Sheet 5 James 5. X2?? flbya 5. I [I2 Vex 021 l. ii"

tiNITED STATES PATENT oFFicE.

5 33. KIRBY, OF.WES'I. RICHFIELD, AND HOYT S. SCOTT, OF CLEVELAND, OHIO;

SAID SCOTT ASSIGNOR TO SAID IKIBBY.

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Application filed. August 5, 1925. Serial at. 48,258.

invention relates to the variable conin. radio reception and has for the provision of a new, simplified oved means for adjusting the caore accurately than heretofore posh the continual increase in the .20 of broadcasting stations, the wave lengths bmitted thereby have become so In order to effect this accurate adjustment.

necessary to separate stations of closely adjacent wave lengths many mechanical expedients have been suggested for effecting slow, regulated. movement of the condenser plates, some of which are impirl'actlcal as requiring undue manipulating s '11 on the part of the user and all of which 'tend to render the instrument unduly complicated and expensive. We have discovered that the same essential result can-be obtained, and this in a much simpler and more ex editious manner by a slight change in the ielectric' value of the condenser by interposing between one or more sets of plates a substance other than air.. This substance maytake the form of a strip of insulating material such as hard rubber, bakelite, mica, etc., or the same may be. formed as a plate or disk adapted to be inserted and removed by rotation of a suitable shaft. v

In the drawings accompanying and form ing a part of thisapplication we have illustrated our improvements as applied to certain well known forms of standard radio condensers, although it will be understood that a great many other forms of construction can be employed within the scope of our invention and that wedo not'limit ourselves to any of the features of-design or arran ement set. forth herein. Fig. 1 is aside e evation of a standard form of variable condenser cohtaining'our improvements; Fig.

2 is a sectional view on the line 22 of Fig. 1 looking in the direction of the arrows; Fig. 8 is a face view of a section of a panel board provided with the device shown in Fig. 1, the internal parts being shown in dotted lines; Fig. 4 illustrates a modified form of our invention applied to a different construction of condenser; Fig. 5 is a central sectional view through another form'of condenser showing another modified form of our invention; Fig. 6 is a plan view of the parts shown in Fig. 5; and Fig. 7 is a sectional view corresponding to the line 77 of Fig. 5 and lookmg in the direction of the arrows.

Variable condensers are made in a great many different shapes, .but generally comprise in some form a pair of spaced frame members 1''l connected by suitable belts or other cross pieces 2. Suitably secured in this frame, sometimes byengagement with the members 2-2 as shown in Figs. 1, 2, 5

and 7, are a plurality of spacedpar'a-llel metal plates 3-3 which constitute one side of the condenser. Tightly secured to a rotatable shaft at which projects through this frame are other spacedmetal plates 5 generally of slightly smaller, size than the plates 3, but arranged so as to project more or less completely between the same as the shaft 4 is rotated. Often times the plates o and 5 are made to approximately semicircular in form as shown in Figs. 1, 2, 5-

and 7, although sometimes they are made of other shapes, such as the logarithmic spiral shown in Fig. 4. This frame is in use ordinarily secured to-the inner side of the panel board 6, the shaft 4, projecting through a hole therein and provided at its end with a knob 7 and dial plate 8 whereby it can be turned and its rotation measured;

In Figs. 1 and 2 we have shown the side members of the frame 1l as 'provided with aligned bearing members 10-10 in which is mounted a rotatable shaft 11 closely adjacent to, but outside of the limits of motion .of the movable plates, and tightly secured to this shaft is a thin plate 12 of some material having a dielectric value other than unity. We have had excellent success with hard rubber for this purpose made in a strip about. 5/100th 'of an inch in thickness, although bakelite, mica, or even glass can be employed or other insulating substance. Preferably, a shown in Figs. 2 and 3, this plate made with long taperingpoint 13 ladapted to ct betweenv the adjacent plates and inthe tormshown in these views we shown another part out the same as formed with a shoulder i ladupted to en- The advantage of making the point 13 long and tapering is that it necessitates a substantial degree of movement of the shaft ll, to eliiect a minor change in the capacity of the condenser and thus constitute a fine advjustment The outer end of the shaft 11 is provided with a suitable knob also preferably graduated to facilitate itsadjustment, which is now being lgcated a short distance from the edge ot'the dial 8.

However, we do not limit ourselves to this particular shape of the-plate 12 since the same may be made semicircular as shown in Fig. 4 or of any other shape desired; and we till do not limit ourselves to the use of only a single plate of dielectric material since plural plates may be employed on the same shalt as illustrated in Fig. 4.

lln Figs. 5 to 7 we have shown another arrangement or parts whereby the shaft carryin the dielectric plate is located concentri- Cally of the condenser for which purpose the main shaft at of the condenser is made hollow and terminated short of the frame mem her 1 Projecting through this hollow shaft is the shaft 11:"- having one end journaled in the frame part l as shown at 20 and having at its. outer end a knob 15 concentric with the knob 7. We have shown the knob 15* as provided with apointer 21 playing over a graduated scale carried by the outer face of the knob 7. The hollow shaft t terminates at the last movable plate 5 and inside oi the last lined plate 3 Tightly secured to the shalt ll at this point is a dielectric plate 12 which is asymmetric in shape so that upon the rotation of the shaft 11 a larger or smaller amount of the same will be inserted between the plates 3 and 5. llt is easyby a device of this character to produce a device wherein it shall require a rotation of the dielectric plate through an arc of several derees to which the capacity or the condenser be an amount equivalentto, the rotation of the movable plates of 1 oar-traction thereof.

lit will be understood that in order to modify the rate of change of the dielectric value it is possible to vary the thicknessof the dielectric plate as well as its pattern and to form apertures therein as shown for e: ample at 22 in Fig. 7, and that'the material or this plate will also influence shape and thickness owing to the wide variations in dielectric strength between different subinvention appears as an attachment to an existing variable condenser, the latter being entirely unchanged. in this embodiment the insulating plate 12 is supported and moved by a shaft member 11 which is secured in operative relation to the condenser by the brackets 10-10, but it will be obvious that the plate 12 can take other forms or be supported and manipulated in other manners and that other means could be. employed for holding the same in proper pdsition relative to. the condenser.

lit will be understood, moreover, that in illustrating certain physical forms in which our invention can conveniently be embodied wedo not propose to limit ourselves to those forms since we claim broadly the method of line tuning of a radio condenser which com.- prises interposing between the plates an adjustablc member having a dielectric value other than unity.

- Having thus described our invention what we claim is: v v

1. The combination with a variable radio condenser having relatively movable metallic plates adjustable to vary the capacity of the condenser, of an auxiliary member of insulating material movable independently of said metallic plates and insertable there between to'vary the dielectric value'ot the condenser and thereby efiect a fine adjustment of the capacity.

.2. lln a radio condenser, the combination with relatively movable metallic plates of a plate of insulating material movable independently of said metallic plates and insertable therebetween to vary the dielectric value of the condenser and thereby efiect a fine adjustment of the capacity.

3. In a variable condensen the combination with metallic plates movable relatively to each other of a member or material having a dielectric value other than unity and means for inserting said member more or less between adjacent metallic plates to vary the dielectric value ot the condenser.

l. in a radio condenser the combination with opposed spaced metallic plates adjacent plates being insulated from each other and alternate plates connected together and movablev bodily with respect to the remainingplatea of a movable member having. a dielectric value. other than unity adapted to be interposed between said first plates to vary the dielectric strength and hence the capacity of the condenser.

5. In a radio condenser the combination with opposed spaced metallic plates, adjacent plates being insulated from each other .and alternate plates connected together, of

varying degrees between said plates upon and alternate plates connected together, of

means for holding said plates in fixed pos1 tion relative to each other, a rotatable shaft journaled at one side of said plates, and a thin plate of insulating material having a dielectric value other than unity carried by said shaft and adapted to be inserted to rotation thereof, said plate having at its margin an elongated tapering point to render the a variation of dielectric value gradual. I a

7. In a variable radio condenser, having fixed and movable metallic plates, a dielectric member niovableindependently of said plates to vary minutely the capacity as determined by the relative positions of said plates.

8. An attachment for variable radio condensers of the type having two sets of metallic plates movable relatively to each other to vary the capacity, said attachment comprising a plate of insulating material adapted to be inserted to a variable extent between certain of said first plates, a memher for supporting and moving said last plate, and means for securing said memberin operative relation to said condenser.

In testimony whereof, we hereunto afiix our signatures.

JAMES B. K'IRBY. HOYT s. SCOTT. 

